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Alternate mark inversion (AMI)

November 2, 2012 10:26 am

Alternate mark inversion (AMI)

Alternate mark inversion (AMI) is a digital transmission technique in which binary values are sent by three voltage states.

  1. ‘0’ bits by a voltage of 0 volts.
  2. ‘1’ bits by a voltage of +V volts or -V volts alternatively

In AMI, zeros are represented by 01 during each bit cell

Ones are represented by 11 or 00, alternately, during each bit cell

A logical “0” is represented by 0 volts; A logical 0 is represented by no symbol

A logical 1 by pulses of alternating polarity.

  • The alternating coding prevents the build-up of a D.C. voltage level down the cable.
  • A logical “1” is represented by either a positive voltage or a negative voltage so that each alternate “1” is represented by a voltage level that is the opposite of that which represented the previous “1”.

The result is a digital waveform that has zero DC voltage on the line.

AMI (Alternate Mark Inversion) is a synchronous clock encoding technique which uses bipolar pulses to represent logical 1 value.

ami

AMI Data Encoding

  • Line-code type used on T1 and E1 circuits.
  • AMI requires that the sending device maintain ones density. Ones density is not maintained independent of the data stream. Sometimes called binary coded alternate mark inversion
  • Typically implemented as a RZ code
  • Little or no DC content in signal
  • Lacks transparency particularly during long sequences of binary ‘0’

 

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yasir

Syed Yasir Hashmi is a tech guru working in the industry for the last 15 years.

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